In this work, we present experimental observations of radiation damage in thermal SiO2 films grown on silicon, induced by energetic (> 0.2 GeV) O, Ni and Xe ions bombardement. The structural analysis of the SiO2 films, using infrared absorption spectroscopy, ellipsometry and etch rate measurements, points to atomic displacements, broken and strained Si-O bonds induced by irradiation. We have also estimated the damage production cross section and the track radii of the ions in the amorphous SiO2 films as a function of the electronic stopping power.

The effect of 4.2 MeV, low dose Si irradiation before annealing of 1 MeV, high dose O-implanted Si has been studied. Si irradiation results in differences in the defect structure both before and after high temperature annealing. With no Si irradiation, annealing results in polycrystalline Si (polySi) formation and microtwinning at the front SiO2/Si interface. With Si irradiation, the polySi volume fraction is greatly reduced after annealing, twinned Si having grown in its place. Si irradiation has no effect on Si inclusions within the SiO2 layer. The dependence of secondary defect formation on Si dose and implant temperature is presented. In particular, Si irradiation at low implant temperatures (150°C) and moderate doses (5×1016 cm−2) is shown to be most effective in the reduction of the polySi volume fraction at the front SiO2/Si interface.

The role of precipitation processes in defect development in high temperature implanted single and multiple implant/anneal SIMOX was studied by transmission electron microscopy. The differences in defect type, density and location were compared. The dominant defects in single implanted and annealed material are pairs of narrow stacking faults (NSFs) at a density of ∼ 106 cm−2 while stacking fault pyramids (SFPs) at a similar density dominate multiple implant/anneal material. However, SFPs are confined to the buried oxide interface and thus the density of through-thickness defects is about two orders of magnitude lower in multiple implant (<104 cm−2) than in single implant material (∼106 cm−2). SFPs are formed from a collection of four NSFs pinned to residual oxide precipitates. This transformation is energetically possible only below a critical NSF length which is dictated by the relative location of the residual precipitates. In turn, the residual precipitate location is determined by the location of as-implanted defects on which SiO2 preferentially nucleates and grows. Thus, the synergistic interaction between precipitation and defect formation and evolution processes plays a key role in determining the final defect microstructure of SIMOX.

To elucidate the mechanism of dose rate (DR) dependence of electrical activation, following two questions are investigated; why the amount of damage remaining after ion bombardment depends on DR and why it affects the electrical activation after high temperature annealing. From the observation that the DR dependence scales with temperature, the activation energy of recovery during ion irradiation has been estimated to be 0.75 and 1.0 eV. A higher DR suppresses the recovery and results in more damage, which in turn delays the electrical activation of implanted impurities.

Concentration profiles of channeling and random implants of boron, phosphorus, and arsenic in silicon are compiled from the literature and are analyzed using Monte Carlo simulations. An empirical 3-parameter model of the electronic stopping power is found which yields excellent results for all channeling directions in the energy range of about 20 keV to 1 MeV. The model contains a local impact parameter dependent part and a nonlocal part, the latter increasing with ion energy. In addition, local electron density dependent stopping power models are investigated, using a realistic electron density distribution obtained by first principles band structure calculations. These models fail to describe the slowing down of ions channeled along the <110> axis.

Heteroepitaxial Si/CoSi2/Si<111> structures were made by high dose implantation of Co in a Si wafer. These single crystaline layers were investigated with 57Co source Mössbauer spectroscopy, 4He ion channeling and X-ray scattering. All results show there is a structural phase transition in the buried CoSi2 layer at a temperature around 200 K.

In this work Si samples implanted with nitrogen (N+ or N2+) at a dose of 1017 cm−2 are characterized by Raman spectroscopy and cross section transmission electron microscopy (XTEM). The correlation between the Raman spectra obtained with different excitation wavelengths and XTEM observations allows to determine the structural features related to the layers contributing to the total spectra. The evolution of these features with the annealing treatments (up to 1150°C) is studied. The results obtained show, after the annealing treatment at the highest temperature, the presence of silicon nitride precipitates in the silicon subsurface region, and the formation of a nitrogen rich polycrystalline Si layer with Si3N4 grains. The Raman spectra from the subsurface region show a remaining shift of -0.15 cm−1 when compared to the spectra from unimplanted Si. This shift, together with the similar shape of both Raman lines, suggests the presence in this region of an average tensile stress of 37.5 MPa.

Fluorine, boron and oxygen implantation in GaAs has been investigated by electrical characterization using current-voltage (I-V), capacitance-voltage (C-V) and deep level transient spectroscopy (DLTS) techniques. Ion implantation at lOOkeV energy was conducted with doses of 1011 and 1012/cm2. Carrier compensation was observed in each implanted sample. The compensation effect strongly depended on ion implantation conditions and ion species. Severe surface damage was also induced which degrades electrical performance. Rapid thermal annealing (RTA) treatment showed the heavier ion implanted samples to be more thermally stable. Defect levels for each implanted species were compared and identified.

We have used molecular-dynamics to investigate the stability and relaxation of point defects — vacancies and interstitials — in a model of amorphous silicon, with the interactions between atoms described by the Stillinger-Weber empirical potential. The annihila-tion of point defects has been proposed as an important mechanism by which relaxation proceeds in amorphous silicon. Starting with a Wooten-Winer-Weaire model of a-Si, we “manually” create vacancies in the structure by removing a number of randomly-selected four-fold coordinated atoms. The system is then allowed to relax. Our calculations reveal unambiguously that, of a number of vacancies introduced in the model at low temperature, roughly a third are stable; these anneal out upon heating at room temperature. The vacancies seem, in most cases, to consist of a relatively large empty volume bounded by four atoms of which at least one is undercoordinated. Our study of interstitials seems to indicate that they diffuse through a “jump-and-bump” process, eventually annihilating when a large enough, properly coordinated, vacant volume is encountered.

By using rapid thermal annealing (RTA) we can obtain a me testable carrier concentration which well exceeds the solid solubility of arsenic dopant in silicon. The deactivation of such the supersaturated dopant, however, may result in relaxation of the metastable concentration. This paper describes lattice location of the deactivated arsenic atoms determined by channeling angular distribution. On the basis of the results for lattice site location the deactivation mechanism of supersaturated As in Si is discussed.

A new method was used to fabricate nanometer-scale structures in Si for photoluminescence (PL) studies. He ions were implanted to form a dense subsurface layer of small cavities (1–8 nm diameters). The implanted specimens were either annealed in H or anodized with HF to evaluate the quantum confinement model for PL from porous Si. Incomplete passivation apparently prevented PL in the H-annealed specimens. Implantation combined with anodization produced a substantial blue shift relative to anodization alone, which is consistent with quantum confinement.

Cross-sectional transmission electron microscopy (XTEM) studies have shown that two distinct damage regions are created when germanium is implanted into single-crystal silicon in high doses and subsequently annealed at high temperatures. The first layer extends approximately 90–95 nm into silicon for an implant energy of 120 keV. The second region is an end-of-range damage region located 200 nm from the silicon surface for the same implantation energy. Neither low-dose, low-energy boron implantation nor the type of cap layers used during annealing alter the damage pattern. Although the dose of the Ge implants is the major factor in the formation of the continuous damage layer, high oxygen concentration at the surface may also contribute to this effect.

The critical point energies, E0, E1 and the Lorentz broadening parameter, Γ, for boron doped p-type silicon were obtained by electrolyte-electroreflectance (EER) at 297K and electron beam electroreflectance (EBER) at 297K and 88K. Electron irradiated samples for fluences of 1014 and 1016 e-/cm2 were compared to the samples before irradiation. The value of the low energy weaker structure, Eo and the higher energy main structure, Ei are obtained by the synthesis of two Lorentz line shapes to fit the experimentally obtained composite spectra. The values as determined by EER were all found to increase with radiation as expected. The values for Eo as found by EBER were consistent with those of EER but those of E1 were not.

The paper presents the results of a comprehensive study of the outdif-fusion of volatile impurities (P, As, Sb) from originally amorphous ion-implanted layers (IILs) of Si at rapid electron-beam heating in vacuum. The phenomenon of enhanced outdiffusion has been discovered and the activation energy of this process has been measured. It has been established that there exists an interconnection between the process of activation, deactivation, diffusion and segregation of the impurity in IIL and its outdiffusion. A qualitative model of the process determining this interconnection has been proposed. The reasons for the lowering of the potential barrier at the IIL-vacuum interface determining the abnormally high rates of vaporization of the impurity have been supposed.

In the p-type shallow junction formation using B+ implantation, preamorphaization is an essential technique to suppress B+ channeling. The crucial problem in this process is defect formation at an amorphous-crystal(a-c) interface. We have demonstrated that MeV ion implantation is effective to reduce defects for shallow junction formation. F+ preimplantation at 40 KeV with 1×l015 cm−2 was effective to form p-type shallow junctions by B+ implantation at 10 KeV with 5×1015cm−2. However, defect formation induced boron diffusion and also leakage current increase. These problems were overcome by MeV ion implantation at 1 MeV F+ or Si+ with 5x×1015 cm−2, followed by rapid thermal annealing at 1000–1100°C for 10 seconds. In the P preimplanted samples, followed by MeV ion implantation, defects at the a-c interface can be reduced and an about 50 % shallower junction depth was obtained, compared with just B+ implanted samples. The results indicate that MeV ion implantation is effective to form a shallow junction with a low leakage current.

The p-n structures was formed by the implantation of Al ions into 6H-SiC n-type films and the thermal annealing. An energy of ions was in the range of 40–90 KeV, an annealing temperature -1700–2100K. We investigated the influence of implantation conditions over the defects electroluminescence of the obtained structures.

After fabricating contacts and mesa-structures with areas 500–500μm our devices showed under the current of 20 mW:

- integral light power 20μW,

- λmax=535 nm, δλmax=80nm.

For the first time was fabricated the green electroluminescence source on SiC with the value of efficiency approximated to one of the A3B5 structures, and after encapsulating it will be possible to obtain LEDs with an integral light power up to 80–100μW.

We have extended our recent work [1,2] on buried suicide formation by Ni diffusion into a buried amorphous silicon layer to the case where silicide formation is at lower temperatures on silicon substrates which have been preamorphized. The reaction of metal atoms from a 12 nm Ni film evaporated on top of a 65 nm thick surface amorphous layer formed by 35 keV Si+ ion implantation has been investigated at temperature ≤400 °C. Rutherford Backscattering Spectrometry (RBS) with channeling, cross-sectional transmission electron microscopy (XTEM), X-ray diffraction and four-point-probe measurements were used to determine the structure, interfacial morphology, composition and resistivity of the silicide films. It has been found that an increased rate of silicidation occurs for amorphous silicon with respect to crystalline areas permitting a selective control of the silicon area to be contacted during silicide growth. Vacuum furnace annealing at 360 °C for 8 hours followed by an additional step at 400 °C for one hour produces a continuos NiSi2 layer with a resistivity 44 μΩ cm.

The formation of a buried IrSi3 layer in (111) oriented Si by ion implantation and annealing has been studied at an implantation energy of 2 MeV for substrate temperatures of 450–550°C. Rutherford backscattering (RBS), ion channeling and cross-sectional transmission electron microscopy showed that a buried epitaxial IrSi3 layer is produced at 550°C by implanting ≥ 3.4 × 1017 Ir/cm2 and subsequently annealing for 1 h at 1000°C plus 5 h at 1100°C. At a dose of 3.4 × 1017 Ir/cm2, the thickness of the layer varied between 120 and 190 nm and many large IrSi3 precipitates were present above and below the film. Increasing the dose to 4.4 × 1017 Ir/cm2 improved the layer uniformity at the expense of increased lattice damage in the overlying Si. RBS analysis of layer formation as a function of substrate temperature revealed the competition between the mechanisms for optimizing surface crystallinity vs. IrSi3 layer formation. Little apparent substrate temperature dependence was evident in the as-implanted state but after annealing the crystallinity of the top Si layer was observed to deteriorate with increasing substrate temperature while the precipitate coarsening and coalescence improved.

Ion Beam Synthesis for SiGe layers was performed to study the end-of-range(EOR) defects and strain-induced dislocations. High Ge doses of 5×1016/cm2, 3×1016/cm2 and 2×1016/cm2 at 120 keV were implanted to obtain 12 at%, 7 at% and 5 at% of Ge peak concentrations respectively. RBS spectra show a projected range(Rp) at a depth of 65nm and an amorphous thickness of 170nm on a wafer with 12 at% of Ge peak concentration. Ge ion implantation was performed both at room temperature(RT) and at liquid nitrogen temperature(LNT), in order to investigate the effect of implantation temperature on reducing EOR defect density. Solid phase epitaxial(SPE) annealing for all SiGe layers was done in nitrogen ambient at 800°C. The EOR defect density is considerably reduced by LNT implantation and the strain-induced dislocations have a threshold Ge peak concentration(about 6 at%) for their abrupt generation. For SiGe layer with 12 at% Ge peak concentration, the amorphous-crystalline(a/c) interfacial morphology changes from a planar interface into a faceted interface during SPE growth at 550°C.

Sub-100 nm P+/N junctions are fabricated by implanting wafers in the plasma immersion ion implantation system (PIII). Ions from SiF4 and BF3 plasmas are implanted at energies from 4–6 keV and 2 keV, respectively. The amorphous region formed by SiF4 im-plantion is shown to be effective in slowing B diffusion during a 10 sec, 1060°C rapid thermal anneal step. Channeling and transmission electron microscopy studies show the recrys-tallized amorphous region is comparable in quality to an unprocessed Si wafer, and the implantation and annealing sequence has no detrimental effects on the physical or electrical characteristics of fabricated devices. Diodes have forward ideality factors of 1.05 to 1.06 and reverse leakage as low as 2 nA/cm2 in the diode bulk at -5 V applied bias.